OBSTRETICS

Diagnosticul prenatal al blocului atrioventricular fetal

 Prenatal diagnosis of fetal atrioventricular heart block

First published: 30 noiembrie 2022

Editorial Group: MEDICHUB MEDIA

DOI: 10.26416/Gine.38.4.2022.7388

Abstract

Fetal atrioventricular heart block (FAVB) is the most com­mon­ly observed type of fetal bradycardia, and is potentially life-threatening. This condition occurs when there is a block­­age in the electrical pathway between the atria and the ven­­tri­­cles of the heart, which can cause the heart to beat too slow or irregularly. This can lead to a range of complications, in­­clu­­ding heart failure, stroke and even death. This pa­per pre­­sents some interesting pictures of FAVB in cases as­so­cia­ted with autoimmune diseases and also some nor­mal re­cor­dings in the hope of a better understanding of this con­di­tion. We intend to provide some usefully vi­sual in­for­ma­tion for clinicians involved in the management of fetal car­dio­vas­cu­lar disorder. The correct diagnosis using the right ul­tra­sound tools and the referral for an echo­car­dio­gra­phy are key factors for a proper management of this con­di­tion. 
 

Keywords
fetal atrioventricular heart block, prenatal diagnosis, causes, fetal echocardiography, M-mode

Rezumat

Blocul atrioventricular (BAV) fetal este una dintre cele mai frec­ven­te tipuri de bradicardie fetală. Este produs de un blocaj în transmiterea semnalului electric dintre atrii şi ventriculi, ceea ce duce la un ritm cardiac mult prea lent sau iregulat. Blo­cul atrio­ven­tri­cu­lar fetal poate cauza o serie de complicaţii, in­clu­zând insuficienţă cardiacă şi chiar moarte fetală intrauterină. Ar­ti­co­lul prezintă câteva cazuri interesante de BAV fetal la pa­­cien­te care prezintă patologie autoimună, în scopul unei mai bu­ne înţelegeri a acestei patologii şi al unui diagnostic prenatal co­rect. Scopul articolului este de a aduce informaţii utile privind di­ag­nos­ti­cul ecografic al acestei patologii. Diagnosticul corect, fo­lo­sind tehnicile potrivite, şi direcţionarea pacientei către un cen­tru de specialitate reprezintă prima etapă în managementul adec­vat al acestei patologii, care poate pune în pericol viaţa fă­tu­lui.
 

Introduction

Fetal atrioventricular heart block (FAVB) is a rare congenital heart condition that affects the electrical signals in the heart. The condition occurs when there is a blockage in the electrical pathway between the atria and the ventricles of the heart, which can cause the heart to beat too slow or irregularly. This can lead to a range of complications, including heart failure, stroke and even death(1).

FAVB is typically diagnosed during pregnancy, using fetal echocardiography, a type of ultrasound that allows doctors to assess the structure and function of the fetal heart. The condition can also be detected after birth, using a variety of diagnostic tests, including electrocardiography (ECG) and cardiac catheterization(2). Ultrasound examination must include the M-mode recording and Power wave Doppler for a correct diagnosis. M-mode ultrasound (also called motion-mode imaging) does not yield full frame images per se, but rather one selected image line is rendered as a function of time. This is used for displaying motion of – for example – the periodic movement of heart valves. Any abnormalities or temporal variations can be directly seen as an image on the screen(4).

The treatment of FAVB depends on the severity of the condition and on the gestational age of the fetus. In some cases, medications may be used to help regulate heart’s rhythm and improve blood flow. In more severe cases, surgery may be necessary to repair the electrical pathway between the atria and the ventricles(3). Steroids are often used. Care should be taken in these cases, as they can further affect the heart, causing pericardial effusion, left ventricular enlargement and poor contractility(5).

In conclusion, FAVB is a rare but serious condition that can have significant consequences for the developing fetus. Early diagnosis and treatment are essential for improving outcomes and for preventing complications. Further research is needed to better understand the causes and the management of FAVB.

Congenital heart block is a condition that occurs when the electrical signals that control the heart’s rhythm are disrupted. This can be caused by a variety of factors, including:

Genetic factors. Congenital heart block can be caused by certain genetic conditions, such as lupus, rheumatoid arthritis or Sjögren’s syndrome, which can affect the development of the heart.

Infections. Infections during pregnancy, such as rubella or cytomegalovirus, can cause congenital heart block.

Medications. Some medications, such as certain types of heart medication or certain types of antibiotics, can increase the risk of congenital heart block.

Environmental factors. Exposure to certain environmental toxins, such as tobacco smoke or some chemicals, during pregnancy can increase the risk of congenital heart block. It’s important to note that, in many cases, the cause of congenital heart block is unknown(6).

Interesting images

We present the case of a 30-year-old female patient with Sjögren’s syndrome and anti-RO antibodies present. In her first pregnancy, she had termination at 24 weeks for complete heart block (Figures 1 and 2).

This is her second pregnancy. Unfortunately, even with hydroxychloroquine prophylaxis at 22 weeks, se­cond- and third-degree block was detected (Figures 3-7).

Figure 1. Four-chamber view in the first pregnancy with complete heart block at 23 weeks and 6 days
Figure 1. Four-chamber view in the first pregnancy with complete heart block at 23 weeks and 6 days
Figure 2. M-mode recording showing simultaneous atrial contrac­tions (arrows pointing down) and ven­tri­cu­lar contraction (arrows pointing up) with complete dissociation in third-degree block
Figure 2. M-mode recording showing simultaneous atrial contrac­tions (arrows pointing down) and ven­tri­cu­lar contraction (arrows pointing up) with complete dissociation in third-degree block
Figure 3. M-mode recording showing simultaneously atrial contractions and ventricular contraction with second heart block and third-degree dissociation
Figure 3. M-mode recording showing simultaneously atrial contractions and ventricular contraction with second heart block and third-degree dissociation
Figure 4. Umbilical artery power Doppler showing a fetal heart rate of 90 bpm, incomplete heart block and intermittent second-degree block
Figure 4. Umbilical artery power Doppler showing a fetal heart rate of 90 bpm, incomplete heart block and intermittent second-degree block
Figure 5. MCA power Doppler showing a fetal heart rate of 80 bpm, incomplete heart block and intermittent second-degree block
Figure 5. MCA power Doppler showing a fetal heart rate of 80 bpm, incomplete heart block and intermittent second-degree block
Figure 6. The same fetus at 32 weeks after dexa­metha­sone, 4 mg, daily. M-mode recording showing 1:1 atrio­ven­tricular transmission and normal ventricular rate
Figure 6. The same fetus at 32 weeks after dexa­metha­sone, 4 mg, daily. M-mode recording showing 1:1 atrio­ven­tricular transmission and normal ventricular rate
Figure 7. For a better understanding of M-mode recor­ding, this image is showing a 1:1 atrioventricular trans­mis­sion and a normal ventricular rate in a normal fetus at 26 weeks of gestation
Figure 7. For a better understanding of M-mode recor­ding, this image is showing a 1:1 atrioventricular trans­mis­sion and a normal ventricular rate in a normal fetus at 26 weeks of gestation

Conclusions

It is extremely important to recognize the condition for a correct management plan. Complete atrioventri­cular block leads to complete dissociation of the atrial and ventricular activity as a result of the damage in the atrioventricular conduction pathways. In patients with third-degree atrioventricular block, the atrial frequency is in the normal range, but the ventricular rate can be lower than 50 beats per minute, usually between 50 and 80 beats/minute. The ultrasound findings in fetal life include ventricular dilatation, reduced ejection fraction, echogenic endocardium located in the left ventricle affecting the mitral valve papillary muscles, and atrioventricular valve causing valve dysfunction. After the suspicion or diagnosis, the patient must be referred for an echocardiography for the exclusion of additional findings and for treatment. The use of M-mode recoding is essential for the diagnosis and it should be used alongside power wave Doppler and 2D imaging of the heart.

Conflict of interests: The authors declare no con­flict of interests.

Bibliografie

  1. Pruetz JD, Miller JC, Loeb GE, Silka MJ, Bar-Cohen Y, Chamait RH. Prenatal diag­no­sis and management of congenital complete heart block. Birth Defects Res. 2019:111(8):380-8.

  2. Simpson J, Vita Z, Miller Owen I. Fetal Cardiology: a practical approach to diag­no­sis and management. London: Springer, 2019.

  3. Hongyo L, Tang C, Qiao L, Zhou K, Li Y. Prenatal management strategy for immune-associated congenital heart block in fetuses. Front Cardiovasc Med. 2021;8:644122.

  4. Mertens LL, Rigby ML, Horowitz ES, Anderson RH. Cross Sectional Echocar­dio­gra­phic and Doppler Imaging. In: Paediatric Cardiology (3th Ed), Churchill Livingstone. 2010:313-39.

  5. Cimpoca-Raptis B, Ciobanu AM, Gică N, Scutelnicu AM, Bouariu A, Popescu M,  Panaitescu AM. Recurrent congenital heart block due to maternal anti-ro antibodies: successful prevention of poor pregnancy outcome with Hydroxychloroquine and added Dexamethasone. Reprod Med. 2022:3(1):36-41.

  6. Hansahiranwadee W. Diagnosis and management of fetal autoimmune atrio­ven­tri­cular block. Int J Womens Health. 2020;2020(12):633-9.

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